järelkõvenemist

Järelkõvenemist, also known as after-hardening or secondary hardening, is a heat treatment process applied to certain types of steel, particularly high-speed steels and some tool steels. It is performed after the initial hardening and tempering stages. The primary purpose of järelkõvenemist is to further increase the hardness and toughness of the steel, especially at elevated temperatures.

This process involves reheating the hardened and tempered steel to a temperature above its original tempering temperature but below its initial hardening temperature. This is typically followed by a rapid cooling. During this reheating phase, fine carbide particles, which may have dissolved during the initial hardening, can precipitate out in a more stable and uniformly dispersed form. This precipitation hardening mechanism contributes significantly to the improved properties.

Järelkõvenemist is crucial for applications where tools or components are subjected to high temperatures during operation, such as cutting tools used in high-speed machining. The increased hardness and wear resistance at elevated temperatures allow these tools to maintain their performance and longevity under demanding conditions. The specific temperatures and holding times for järelkõvenemist vary depending on the steel composition and the desired final properties. It is a critical step in achieving the optimal performance characteristics of specialized steels.